Movie: This is Spinal Tap (1983)
In director Rob Reiner's classic, alarmingly realistic music industry satire This is Spinal Tap, Reiner's three co-writers—Christopher Guest, Harry Shearer, and Michael McKean—play the aloof, self-involved members of the chart-topping British rock group Spinal Tap. Idiotic frontman Nigel Tufnel (Guest) brings documentarian Marty DiBergi (Reiner) into his guitar room to show the filmmaker all of his musical toys.
Nigel's prized possession is an amplifier on which all of the various nobs go "up to 11," while most, if not all, other amps go up to 10. Marty can't help but ask if that numerical oddity means that Nigel's amp is louder than others, to which the rocker replies, "It's one louder…. Most blokes play on their guitar, and they get to 10—where can you go from there? Nowhere!"
To get "that extra push over the cliff, the Spinal Tap fellas put their amp to 11, a pointless strategy that Marty questions with, "Why don't you just make 10 louder and make 10 be the top number and make that a little louder." Nigel looks bewildered: "These go to 11."